/*
 * (MPSAFE)
 *
 * Copyright (c) 1982, 1986, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)vm_swap.c   8.5 (Berkeley) 2/17/94
 * $FreeBSD: src/sys/vm/vm_swap.c,v 1.96.2.2 2001/10/14 18:46:47 iedowse Exp $
 */

#include "opt_swap.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysmsg.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/nlookup.h>
#include <sys/sysctl.h>
#include <sys/dmap.h>           /* XXX */
#include <sys/vnode.h>
#include <sys/fcntl.h>
#include <sys/blist.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/conf.h>
#include <sys/stat.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/swap_pager.h>
#include <vm/vm_zone.h>
#include <vm/vm_param.h>

#include <sys/mutex2.h>
#include <sys/spinlock2.h>

/*
 * Indirect driver for multi-controller paging.
 */

#ifndef NSWAPDEV
#define NSWAPDEV        4
#endif
static struct swdevt should_be_malloced[NSWAPDEV];
struct swdevt *swdevt = should_be_malloced;     /* exported to pstat/systat */
static swblk_t nswap;           /* first block after the interleaved devs */
static struct mtx swap_mtx = MTX_INITIALIZER("swpmtx");
int nswdev = NSWAPDEV;                          /* exported to pstat/systat */
swblk_t vm_swap_size;
swblk_t vm_swap_max;

static int swapoff_one(int index);
struct vnode *swapdev_vp;

/*
 * (struct vnode *a_vp, struct bio *b_bio)
 *
 * vn_strategy() for swapdev_vp.  Perform swap strategy interleave device
 * selection.
 *
 * This function supports the KVABIO API.  If the underlying vnode/device
 * does not, it will make appropriate adjustments.
 *
 * No requirements.
 */
static int
swapdev_strategy(struct vop_strategy_args *ap)
{
        struct bio *bio = ap->a_bio;
        struct bio *nbio;
        struct buf *bp = bio->bio_buf;
        swblk_t sz, off, seg, blkno, nblkno;
        int index;
        struct swdevt *sp;
        sz = howmany(bp->b_bcount, PAGE_SIZE);
        blkno = (swblk_t)(bio->bio_offset >> PAGE_SHIFT);

        /*
         * Convert interleaved swap into per-device swap.  Note that
         * the block size is left in PAGE_SIZE'd chunks (for the newswap)
         * here.
         */
        nbio = push_bio(bio);
        if (nswdev > 1) {
                off = blkno % SWB_DMMAX;
                if (off + sz > SWB_DMMAX) {
                        bp->b_error = EINVAL;
                        bp->b_flags |= B_ERROR;
                        biodone(bio);
                        return 0;
                }
                seg = blkno / SWB_DMMAX;
                index = seg % nswdev;
                seg /= nswdev;
                nbio->bio_offset = (off_t)(seg * SWB_DMMAX + off) << PAGE_SHIFT;
        } else {
                index = 0;
                nbio->bio_offset = bio->bio_offset;
        }
        nblkno = (swblk_t)(nbio->bio_offset >> PAGE_SHIFT);
        sp = &swdevt[index];
        if (nblkno + sz > sp->sw_nblks) {
                bp->b_error = EINVAL;
                bp->b_flags |= B_ERROR;
                /* I/O was never started on nbio, must biodone(bio) */
                biodone(bio);
                return 0;
        }
        if (sp->sw_vp == NULL) {
                bp->b_error = ENODEV;
                bp->b_flags |= B_ERROR;
                /* I/O was never started on nbio, must biodone(bio) */
                biodone(bio);
                return 0;
        }

        /*
         * Issue a strategy call on the appropriate swap vnode.  Note that
         * bp->b_vp is not modified.  Strategy code is always supposed to
         * use the passed vp.
         *
         * We have to use vn_strategy() here even if we know we have a
         * device in order to properly break up requests which exceed the
         * device's DMA limits.
         */
        vn_strategy(sp->sw_vp, nbio);

        return 0;
}

static int
swapdev_inactive(struct vop_inactive_args *ap)
{
        vrecycle(ap->a_vp);
        return(0);
}

static int
swapdev_reclaim(struct vop_reclaim_args *ap)
{
        return(0);
}

/*
 * Create a special vnode op vector for swapdev_vp - we only use
 * vn_strategy(), everything else returns an error.
 */
static struct vop_ops swapdev_vnode_vops = {
        .vop_default =          vop_defaultop,
        .vop_strategy =         swapdev_strategy,
        .vop_inactive =         swapdev_inactive,
        .vop_reclaim =          swapdev_reclaim
};
static struct vop_ops *swapdev_vnode_vops_p = &swapdev_vnode_vops;

VNODEOP_SET(swapdev_vnode_vops);

/*
 * swapon_args(char *name)
 *
 * System call swapon(name) enables swapping on device name,
 * which must be in the swdevsw.  Return EBUSY
 * if already swapping on this device.
 *
 * No requirements.
 */
int
sys_swapon(struct sysmsg *sysmsg, const struct swapon_args *uap)
{
        struct thread *td = curthread;
        struct vattr attr;
        struct vnode *vp;
        struct nlookupdata nd;
        int error;

        error = caps_priv_check_self(SYSCAP_RESTRICTEDROOT);
        if (error)
                return (error);

        mtx_lock(&swap_mtx);
        vp = NULL;
        error = nlookup_init(&nd, uap->name, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vref(&nd.nl_nch, nd.nl_cred, &vp);
        nlookup_done(&nd);
        if (error) {
                mtx_unlock(&swap_mtx);
                return (error);
        }

        if (vn_isdisk(vp, &error)) {
                error = swaponvp(td, vp, 0);
        } else if (vp->v_type == VREG && vp->v_tag == VT_NFS &&
                   (error = VOP_GETATTR(vp, &attr)) == 0) {
                /*
                 * Allow direct swapping to NFS regular files in the same
                 * way that nfs_mountroot() sets up diskless swapping.
                 */
                error = swaponvp(td, vp, attr.va_size / DEV_BSIZE);
        }
        if (error)
                vrele(vp);
        mtx_unlock(&swap_mtx);

        return (error);
}

/*
 * Swfree(index) frees the index'th portion of the swap map.
 * Each of the nswdev devices provides 1/nswdev'th of the swap
 * space, which is laid out with blocks of SWB_DMMAX pages circularly
 * among the devices.
 *
 * The new swap code uses page-sized blocks.  The old swap code used
 * DEV_BSIZE'd chunks.
 *
 * XXX locking when multiple swapon's run in parallel
 */
int
swaponvp(struct thread *td, struct vnode *vp, u_quad_t nblks)
{
        swblk_t aligned_nblks;
        int64_t dpsize;
        struct ucred *cred;
        struct swdevt *sp;
        swblk_t vsbase;
        swblk_t dvbase;
        cdev_t dev;
        int index;
        int error;
        swblk_t blk;

        cred = td->td_ucred;

        lwkt_gettoken(&vm_token);       /* needed for vm_swap_size and blist */
        mtx_lock(&swap_mtx);

        /*
         * Setup swapdev_vp.  We support the KVABIO API for this vnode's
         * strategy function.
         */
        if (!swapdev_vp) {
                error = getspecialvnode(VT_NON, NULL, &swapdev_vnode_vops_p,
                                    &swapdev_vp, 0, 0);
                if (error)
                        panic("Cannot get vnode for swapdev");
                swapdev_vp->v_type = VNON;      /* Untyped */
                vsetflags(swapdev_vp, VKVABIO);
                vx_unlock(swapdev_vp);
        }

        for (sp = swdevt, index = 0 ; index < nswdev; index++, sp++) {
                if (sp->sw_vp == vp) {
                        error = EBUSY;
                        goto done;
                }
                if (!sp->sw_vp)
                        goto found;

        }
        error = EINVAL;
        goto done;
    found:
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        error = VOP_OPEN(vp, FREAD | FWRITE, cred, NULL);
        vn_unlock(vp);
        if (error)
                goto done;

        /*
         * v_rdev is not valid until after the VOP_OPEN() call.  dev_psize()
         * must be supported if a character device has been specified.
         */
        if (vp->v_type == VCHR)
                dev = vp->v_rdev;
        else
                dev = NULL;

        if (nblks == 0 && dev != NULL) {
                dpsize = dev_dpsize(dev);
                if (dpsize == -1) {
                        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                        VOP_CLOSE(vp, FREAD | FWRITE, NULL);
                        vn_unlock(vp);
                        error = ENXIO;
                        goto done;
                }
                nblks = (u_quad_t)dpsize;
        }
        if (nblks == 0) {
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                VOP_CLOSE(vp, FREAD | FWRITE, NULL);
                vn_unlock(vp);
                error = ENXIO;
                goto done;
        }

        /*
         * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks.
         * First chop nblks off to page-align it, then convert.
         * 
         * sw->sw_nblks is in page-sized chunks now too.
         */
        nblks &= ~(u_quad_t)(ctodb(1) - 1);
        nblks = dbtoc(nblks);

        /*
         * Post-conversion nblks must not be >= BLIST_MAXBLKS, and
         * we impose a 4-swap-device limit so we have to divide it out
         * further.  Going beyond this will result in overflows in the
         * blist code.
         *
         * Post-conversion nblks must fit within a (swblk_t), which
         * this test also ensures.
         */
        if (nblks > BLIST_MAXBLKS / nswdev) {
                kprintf("exceeded maximum of %ld blocks per swap unit\n",
                        (long)BLIST_MAXBLKS / nswdev);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                VOP_CLOSE(vp, FREAD | FWRITE, NULL);
                vn_unlock(vp);
                error = ENXIO;
                goto done;
        }

        sp->sw_vp = vp;
        sp->sw_dev = devid_from_dev(dev);
        sp->sw_device = dev;
        sp->sw_flags = SW_FREED;
        sp->sw_nused = 0;

        /*
         * nblks, nswap, and SWB_DMMAX are PAGE_SIZE'd parameters now, not
         * DEV_BSIZE'd.   aligned_nblks is used to calculate the
         * size of the swap bitmap, taking into account the stripe size.
         */
        aligned_nblks = (swblk_t)((nblks + SWB_DMMASK) &
                                  ~(u_swblk_t)SWB_DMMASK);
        sp->sw_nblks = aligned_nblks;

        if (aligned_nblks * nswdev > nswap)
                nswap = aligned_nblks * nswdev;

        if (swapblist == NULL)
                swapblist = blist_create(nswap);
        else
                blist_resize(&swapblist, nswap, 0);

        for (dvbase = SWB_DMMAX; dvbase < aligned_nblks; dvbase += SWB_DMMAX) {
                blk = min(aligned_nblks - dvbase, SWB_DMMAX);
                vsbase = index * SWB_DMMAX + dvbase * nswdev;
                blist_free(swapblist, vsbase, blk);
                vm_swap_size += blk;
                vm_swap_max += blk;
        }
        swap_pager_newswap();
        error = 0;
done:
        mtx_unlock(&swap_mtx);
        lwkt_reltoken(&vm_token);
        return (error);
}

/*
 * swapoff_args(char *name)
 *
 * System call swapoff(name) disables swapping on device name,
 * which must be an active swap device. Return ENOMEM
 * if there is not enough memory to page in the contents of
 * the given device.
 *
 * No requirements.
 */
int
sys_swapoff(struct sysmsg *sysmsg, const struct swapoff_args *uap)
{
        struct vnode *vp;
        struct nlookupdata nd;
        struct swdevt *sp;
        int error, index;

        error = caps_priv_check_self(SYSCAP_RESTRICTEDROOT);
        if (error)
                return (error);

        mtx_lock(&swap_mtx);
        vp = NULL;
        error = nlookup_init(&nd, uap->name, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vref(&nd.nl_nch, nd.nl_cred, &vp);
        nlookup_done(&nd);
        if (error)
                goto done;

        for (sp = swdevt, index = 0; index < nswdev; index++, sp++) {
                if (sp->sw_vp == vp)
                        goto found;
        }
        error = EINVAL;
        goto done;
found:
        error = swapoff_one(index);
        swap_pager_newswap();

done:
        mtx_unlock(&swap_mtx);
        return (error);
}

static int
swapoff_one(int index)
{
        swblk_t blk, aligned_nblks;
        swblk_t dvbase, vsbase;
        u_int pq_active_clean, pq_inactive_clean;
        struct swdevt *sp;
        struct vm_page marker;
        vm_page_t m;
        int q;

        mtx_lock(&swap_mtx);

        sp = &swdevt[index];
        aligned_nblks = sp->sw_nblks;
        pq_active_clean = pq_inactive_clean = 0;

        /*
         * We can turn off this swap device safely only if the
         * available virtual memory in the system will fit the amount
         * of data we will have to page back in, plus an epsilon so
         * the system doesn't become critically low on swap space.
         */
        for (q = 0; q < PQ_L2_SIZE; ++q) {
                bzero(&marker, sizeof(marker));
                marker.flags = PG_FICTITIOUS | PG_MARKER;
                marker.busy_count = PBUSY_LOCKED;
                marker.queue = PQ_ACTIVE + q;
                marker.pc = q;
                marker.wire_count = 1;

                vm_page_queues_spin_lock(marker.queue);
                TAILQ_INSERT_HEAD(&vm_page_queues[marker.queue].pl,
                                  &marker, pageq);

                while ((m = TAILQ_NEXT(&marker, pageq)) != NULL) {
                        TAILQ_REMOVE(&vm_page_queues[marker.queue].pl,
                                     &marker, pageq);
                        TAILQ_INSERT_AFTER(&vm_page_queues[marker.queue].pl, m,
                                           &marker, pageq);
                        if (m->flags & (PG_MARKER | PG_FICTITIOUS))
                                continue;

                        if (vm_page_busy_try(m, FALSE) == 0) {
                                vm_page_queues_spin_unlock(marker.queue);
                                if (m->dirty == 0) {
                                        vm_page_test_dirty(m);
                                        if (m->dirty == 0)
                                                ++pq_active_clean;
                                }
                                vm_page_wakeup(m);
                                vm_page_queues_spin_lock(marker.queue);
                        }
                }
                TAILQ_REMOVE(&vm_page_queues[marker.queue].pl, &marker, pageq);
                vm_page_queues_spin_unlock(marker.queue);

                marker.queue = PQ_INACTIVE + q;
                marker.pc = q;
                vm_page_queues_spin_lock(marker.queue);
                TAILQ_INSERT_HEAD(&vm_page_queues[marker.queue].pl,
                                  &marker, pageq);

                while ((m = TAILQ_NEXT(&marker, pageq)) != NULL) {
                        TAILQ_REMOVE(
                                &vm_page_queues[marker.queue].pl,
                                &marker, pageq);
                        TAILQ_INSERT_AFTER(
                                &vm_page_queues[marker.queue].pl,
                                m, &marker, pageq);
                        if (m->flags & (PG_MARKER | PG_FICTITIOUS))
                                continue;

                        if (vm_page_busy_try(m, FALSE) == 0) {
                                vm_page_queues_spin_unlock(marker.queue);
                                if (m->dirty == 0) {
                                        vm_page_test_dirty(m);
                                        if (m->dirty == 0)
                                                ++pq_inactive_clean;
                                }
                                vm_page_wakeup(m);
                                vm_page_queues_spin_lock(marker.queue);
                        }
                }
                TAILQ_REMOVE(&vm_page_queues[marker.queue].pl,
                             &marker, pageq);
                vm_page_queues_spin_unlock(marker.queue);
        }

        if (vmstats.v_free_count + vmstats.v_cache_count + pq_active_clean +
            pq_inactive_clean + vm_swap_size < aligned_nblks + nswap_lowat) {
                mtx_unlock(&swap_mtx);
                return (ENOMEM);
        }

        /*
         * Prevent further allocations on this device
         */
        sp->sw_flags |= SW_CLOSING;
        for (dvbase = SWB_DMMAX; dvbase < aligned_nblks; dvbase += SWB_DMMAX) {
                blk = min(aligned_nblks - dvbase, SWB_DMMAX);
                vsbase = index * SWB_DMMAX + dvbase * nswdev;
                vm_swap_size -= blist_fill(swapblist, vsbase, blk);
                vm_swap_max -= blk;
        }

        /*
         * Page in the contents of the device and close it.
         */
        if (swap_pager_swapoff(index) && swap_pager_swapoff(index)) {
                mtx_unlock(&swap_mtx);
                return (EINTR);
        }

        vn_lock(sp->sw_vp, LK_EXCLUSIVE | LK_RETRY);
        VOP_CLOSE(sp->sw_vp, FREAD | FWRITE, NULL);
        vn_unlock(sp->sw_vp);
        vrele(sp->sw_vp);
        bzero(swdevt + index, sizeof(struct swdevt));

        /*
         * Resize the bitmap based on the nem largest swap device,
         * or free the bitmap if there are no more devices.
         */
        for (sp = swdevt, aligned_nblks = 0; sp < swdevt + nswdev; sp++) {
                if (sp->sw_vp)
                        aligned_nblks = max(aligned_nblks, sp->sw_nblks);
        }

        nswap = aligned_nblks * nswdev;

        if (nswap == 0) {
                blist_destroy(swapblist);
                swapblist = NULL;
                vrele(swapdev_vp);
                swapdev_vp = NULL;
        } else {
                blist_resize(&swapblist, nswap, 0);
        }

        mtx_unlock(&swap_mtx);
        return (0);
}

/*
 * Account for swap space in individual swdevt's.  The caller ensures
 * that the provided range falls into a single swdevt.
 *
 * +count       space freed
 * -count       space allocated
 */
void
swapacctspace(swblk_t base, swblk_t count)
{
        int index;
        swblk_t seg;

        vm_swap_size += count;
        seg = base / SWB_DMMAX;
        index = seg % nswdev;
        swdevt[index].sw_nused -= count;
}

/*
 * Retrieve swap info
 */
static int
sysctl_vm_swap_info(SYSCTL_HANDLER_ARGS)
{
        struct xswdev xs;
        struct swdevt *sp;
        int     error;
        int     n;

        error = 0;
        for (n = 0; n < nswdev; ++n) {
                sp = &swdevt[n];

                xs.xsw_size = sizeof(xs);
                xs.xsw_version = XSWDEV_VERSION;
                xs.xsw_blksize = PAGE_SIZE;
                xs.xsw_dev = sp->sw_dev;
                xs.xsw_flags = sp->sw_flags;
                xs.xsw_nblks = sp->sw_nblks;
                xs.xsw_used = sp->sw_nused;

                error = SYSCTL_OUT(req, &xs, sizeof(xs));
                if (error)
                        break;
        }
        return (error);
}

SYSCTL_INT(_vm, OID_AUTO, nswapdev, CTLFLAG_RD, &nswdev, 0,
           "Number of swap devices");
SYSCTL_NODE(_vm, OID_AUTO, swap_info_array, CTLFLAG_RD, sysctl_vm_swap_info,
            "Swap statistics by device");